Do I need to use a pre-processed dataset to classify comments?
Here's a list of some of the best python libraries for natural language processing.


Natural Language Toolkit (nltk)
Covers all the basic functions and NLP tools such as tokenization etc.
TextBolb
This is a good library of beginners, it provides the nltk toolkit in a simplified format.
Spacy
It is an advanced library and can be used in production code.


You can preprocess textual data in a number of ways. It depends on the type of task at hand and the size of the data.

From your question, I think you are referring to converting the words to a vector form word2vec. Here is a massive word2vect list from Google.

Also have a look at preprocessing techniques in NLP such as tf-idf etc.